The noise produced by the fume extracting hoods is originated by the fan and the vibrations which it's functioning may provoke. Generally, the hoods dispose of a control unit that permits to vary the speed of the fan, and thus the capacity of extraction, Depending on the type of the hood, be it of domestic or of industrial type, of the power of the fan and of the selected speed in each moment, it will depend on the noise produced.
For the amenity of the users it is desirable to eliminate or at least to reduce this noise. Therefore it is already known through the patent EP 0596846 to provide the hood with means for the active absorption of the sound, whose means consist of an acoustic sensor that measures the level of the noise, of a loudspeaker to emit a tone that silences a sound of the fan in inverse phase with itself, and of an electronic control unit connected to said sensor and loudspeaker and adapted to control the loudspeaker in response to the information received from the sensor. This set up is complicated and considerably increases the costs of the hood, apart from presenting problems of assembling and functioning.